Vacuum servo brake



i@ 1932. l G. P. BERRY VACUUM sERvo BRAKE GEORGE?. BERRY, oE DETROIT, MICHIGAN, AssGNon 'ro GENERAL Brannon,

Patented Aug. 16, 1932 U-Nrreo 1 STATES v1: TENT GFICE e. l

ooRrna'rIomor DETROIT, MICHIGAN, A conronn'IoN or DELAWARE VACUUM SEBVO :BRAKE Application 'mea-August 17, laaafserinl no. '$59,502.

This invention relates to fluid pressureoperated brakes wherein fluid pressure means is used as a Servo brake operating device under. the control of the operator to apply th(` brakes. Among theobjects of the invention are lirst tosimplify the structure whereby the auxilliary power means is rendered active; second, to so design thestructure that there shall be no braking action effected directly by the mechanical effort applied by the operator until after the maximum action of the. vServo brake mechanism ;rtl1ird, to design an operating mechanism so that the power brake shall give a reaction on the pedal against the manually applied force of the operator in` proportion to they intensity of the power braking instrumentality; fourth, to construct a novel brake applying means wherein the fluid pressure means may, under no circiunstances, move the pedal'in the direction of brake application; fth, to so design the structure that at any time when the fluid pressure fails the brake may be applied by the application of theJ manual force through a direct mechanical connection, and also when the Servo brake is in operation at its maximum, further force may be applied by additional etl'ort on the part of theoperator. Other objects and advantages will be understood from the following description.

In the drawings, accompanying this de-` -scri ption, Figure 1 is a, view in side elevation partly in section. Figure 2 is a. longitudinal section through the power operating mechanism. Figure 3 is a side elevation of the assembled, pedal and brake lever. Figure 4 is a View substantially on line 1-4= of Figure 3. In general theinvention comprises a power cylinder, a valve, al brake lever, anda pedal.

The power cylinder includes a reciprocating member which is to be connected to the brake lever and by its movement to actuate the brakes through the rotation of the brake lever. The valve controls the admission of sub- 45' atmospheric pressure to the power cylinder, this sub-atmospheric pressure being conveniently obtained from an engine manifold as is usual. The pedal is designed primarily to control the valve and incidentally to afford the means whereby vthe operator may supplement" the action ofthe power brake when the latter is operating at its4 maximum intensity.

The drawings show the several parts `but omit the connection of the conduitl from the valve to the source of suction. Referring by reference characters to the drawings numeral 5 isl the pedal. It will be understood, of course, that in place of a. pedal any manually operated `lever may be used. Thel pedal is provided with a foot engagement `pa1-t7 and is rotatably supported upon a shaft 9, preferably by the use of roller bearings 8. The pedal has a second arm comprising forks'll. This arm is positioned somewhat above the pivot shaft 9. Another forked arm 13 is p0- sitioned below the pivot shaft 9 and carries an extension in the form of a stamping 15 secured to the fork ends 13 as by 4fastening shown in Figure 3. Lever arm 13 is also provided with a screw or other adjusting member 12 to engage a fixed part 14, these parts 13 and 14 serving to limit the counter-clock- Wise rotation, or release movement of the pedal, What may be termed a brake lever is representedon the drawings by numeral 22. It has a central opening whichfis somewhat larger than the outer ring of bearing 8 and which opening surrounds that bearing. A pivotpin 23 is secured to the pedal arm 11 and rotatably supports the brake lever. Rotation of the brake .lever about pivot 23 is limited by the engagement with the bearing ring at either oney of two points of contact a or b as the lever swings about its pivot pin. Upwardly of pivot 23 the brake lever has a. plurality of openings 27 for connection at either of these points with a brake rod 28.

This rod 28 is merely illustrative of any oonas'shown at 31, its forked ends straddling the lower end of stamping 15. v The power unit or power cylinder may be conveniently constructed from two conical parts 33 and 35. These two parts have their larger diameter portions secured together by suitable fastening means 37 Part 33 may be anchored by a bracket 39 secured to any convenient part of the vehicle as, for example, the channel frame member 41. The anchor consists of the member 43 secured in an convenient manner to part 39 and itself pivoted as at 45 to a lug 47 carried by part 33.` 'Part 35 at its smaller end carries a piston guiding sleeve 49. A folding conical diaphragm 51 `is clamped at its outer peripheral portion between parts 33 and 35 as shown in the drawkao ings.r Its inner and smaller periphery is clamped between a rigid reciprocating `plunger 53 and a cooperating ring 55.

lunger 53 has a sleeve portion 57 which 'is rigidly secured toa hollow piston rod 59.

Suitable openings 61 admit air at all times to `the spacer within the power cylinder at one side, the right side, of the diaphragm, as shown in Figure 2. Piston rod 59 at its outer end isv provided with a threaded sleeve 63 forked as at 65, its forked ends being secured by fastening means 67 to any one of a plurality of openings 68 in the ends'of the brake lever. Within the tubular piston rod 59 is a concentric tube 69 forming an annular space 71 between these two'tubular members. Adjacentthe outer ends of tubes 59 and 69 the annular space is closed in any way found convenient. It is also'closed at the inner ends of these parts as shown in Figure 2 where the outer part/'59 is made in the form of a head closing the annular space and tapered to form a valve seat 7 3.

An inlet pipe 75 extending from the manifold of the engine or other source of suction not illustrated, communicates by means of an opening 77 in a ring 79 secured to the vpiston rod and suitable openings in piston rod with the annular space as will be clear from an inspection of the drawings. The suction from the manifold is transmitted fromy the manifold through the pipe 75 into the annular space 71 and to the left side of the diaphragm 51 when permitted to do so by the action of the valve described below. The valve in the present instancewis preferably formed as a part of the power unitgand incorporated therein. It includes a valve member 81 whichas shown is slidable on the inner end of the pistonvrod 59. This valve member 81 is formed with an internal groove 83 near itsinner end, the extreme inner end of theL valve being provided with a valve face 85 which vcooperates withthe valve seat 73 to cut ofi the supply of suction from the manifold to the power cylinder. Suitable openings 87 in piston rod 59 afford communication betweenvthe annular space 71 and the groove 83. Since the pressure conditions in the groove are operating equally upon both ends of the groove these pressure conditions have no tendency to move the valve 8l in either direction andthe valve may be said to be pressure balanced and is only moved by application of extraneous forces. When the valve 81 is moved to the left from the position shown in Figure 2 the face 85 is raised from the valve seat 73. The valve is thereforeunseated and it will be obvious that the suction of the manifold is in communication with that part of the cylinder to the left of the diaphragm. This movement of unseating the valve is effected by a rod 89 which is mounted to reciprocate through the inner tube 69. The movement is produced by engagement of the outer end of the rod 89 with one of the recesses 21 of the stamping 15. It will be understood that the plurality of recesses 21 are provided to correspond with the plurality of openings 68 to which the forked member of the piston rod may be attached. The inner end of rod 89 is attached to the center of the bottom of a cupped member 93. Passin through the bottom of the cup and spaced rom its center are a plurality of bolts 95 with heads 97. These bolts extend through openings in the cup and are threaded into the valve member 81 as clearly shown in Figure 2. Movement of the cup 93 inwardly of the lpower cylinder causes the bottom of the cup to engage heads 97 and move'the valve'81 in a similar inward direction whereby the valveis unseated. The annular flanges of the ctp 93 represented by numeral 99 engage shoulders 101 on a circular series of bolts 103. Bolts 103 are guided in the openings in the plunger 53 and a valve ring 105 is carried by these bolts between the heads thereof and the second series of shoulders 107. By this means the ring 105 is held from movement axiall'y along the bolt andv also in spaced relation to the flanges 99 of the cup. Ring 105 is designed to at times close a series of openings 108 in the plunger 53. Surrounding the bolts are springs 109 engaging the flange 99 and suitable abutments on the end of the bolts. A spring 113 surrounds the inner .end of the valve 81 engaging a shoulder on said valve member and the inner portion o f the bottom of the cup. Surrounding the outer end of rod89 there is as shown a spring 119 normally pressing the rod outwardly so that its extreme end engages the recesses 21 as explained above.

- and lever in these positions, the spring 113 the pedal.

insures the closure of the suction valve while the pressure of the spring 119 through rod 89 pulls the air valve open. It now it is desired to apply the brake, the pedal isdepressed turning clockwise. If spring 29 is used and offers at the start greater resistance than does the taking up of clearance at the brakes, the pedal 5 and the lever 22 move as a unit durmg this initial action of The resistance at the brake then becomes greater than that of spring 29 With the result that the pedal turns relatively to the brake lever. In so 'doing the point 27 acts as a fulcrum for lever 22. Lever 22 is rotated in a counter-clockwise direction about its fulcrum 27 by clockwise rotation of the pedal acting upon the brake lever 22 by the connecting pin 23. This movement results in the breaking of the contact at a and the contact at b is approached. When the Contact at a is broken, the rod 89 closes the air valve. The next increment of mo tion causes the cup 93 to engage the heads 97 and the suction valve opens. These valve actions occur while the points a and b are both out of contact. The plunger 53 is then in an unbalanced position between subatmospheric pressure at its left, and 'at'- mospheric pressure onl itsright side. It

therefore moves inwardly in the power cylinder. This tends to cause a pull through the piston rod 59 on the lower end of tie brake lever 22 and the power brake is actuated. The operation may perhaps bcstbe understood by assuming that point 27 is the ulcrum of lever 22. The developing suction in the power cylinderr` is operating to rotate the pull in a counter-clockwise direction through its connection at 23. When this developed force is 'suiiicient to balance the pedal pressure, the inward movement of 59 has causedthe engagement of the valve members 73 and 85 and the suction valve is closed. The manually applied pressure at the pedal with its long leverage balances the forces acting'at points 27 and at thc lower end of the brake lover, and the operator easily resists the tension on the brake rods and feels the intensity of the -powcr brake. This action of automatically cutting ofi the source of suction `is not attended b v the opening of the air valveunless the operator removes his foot from the pedal. Therefore the brakes remain applied with a predeter- Imined degree of intensity which is measured by the resistance felt by the operator on the y foot pad 7'. They lmay be released b y the removal of the pressure at 7 whereupon the spring 119 opens the air valve7 or additional fluid pressure braking action may be secured by a further depression of the pedal whereupon the action occurs as before. It will also be understood that a diminution of pressure on the pedal will be attended by a proportionate reduction of the intensity of the force'applied by the vacuum Servo device. It should be observed that infso a plyingthe brake the operator has done notliing but control the valve. N o part of his' manually applied force has directly operated on the brake. rod 28 and in piston rod 59 constitute forces acting upon pivot 23 tending to rotate the pedal counter-clockwise which forces are resisted by the manual effort on the pedal. The effort required is but little, the long leverage ofthe pedal as'compared with the short arm between pivot 23 and the pedal pivot 9. The feel is therefore present and is in proportion to the intensity of the power brake. Again and particularly important the power brake insofar asitaifects the pedal never tends to move it in the direction of brake application. The only influence is one tending to move it against the force exerted by the operator. There is never a tendency of the pedal to move from the foot of the operator which movement isfcharacteristic of some of the power brakes. Only when the brake lever reaches its second contact at b can manualeffort beapplied to actuate the brake directly. When so in con-v tact at vb the brake lever and the pedal act as one. This may occur if the suction brake for-any means is inoperative.` It may also occur at any time while the suction brake is operating at its maximum, by depressingthe pedalv suiiiciently not only t0 keep up with the rotation of the brake lever, but to maintain the contact between the brake lever and the pedal at' b whereupon any desired manual effort may be added to the Servo brake.

Incidental to theconstruction, it should be noted that the pressure condition within the groove ofthe valve memberv 81 is effect-ive in both directions so that the valve itself is in balanced condition and has no tendency to move oneway or the other except by app ication of extraneous forces. It will also be seen that thesprings 109 permit the cup to be moved inwardly and the suction valve to open after the'air valve has been closed. The springs 113 insure the closing of the suction valve when the parts are in position to permit it toso function. The construction is extremely simple, occupying but `little more room than the ordinary pedal. Compactness is also attained by the incorporation of the valve Awithin the power unit and by the concentric'relation of the operating rod 89 withowing tol The tension in the brake in the piston rod 59.` By the arrangement of the double conical power cylinder with the foldable diaphragm a comparatively long stroke is given the piston and its rod such as could not occur were the diaphragm-substantially flat.

It may be explained that the springr29 op- I erates tofpermit the clearance 'at the brake to be taken up* before the relative movement between the pedal and the brake lever introduce the suction brake operating imechanism.

This spring may be omitted if desired. In

. movable part connected to said second member and a control device for rendering said power element active, mechanism moved by said manually operated member to actuate said control device.

2. In Servo power mechanism, a manually operated member, a fulcrum therefor, a seclond member pivoted to said first named member and surrounding with a clearance the said fulcrurn, a. brake applying rod connected to said second member on one side of its pivot,

a power device-,llaving a movable, part connected to said second` .member to rotate it about its pivot with the manually operable member, a valve to control said power d'evice and movable means moved by said manually operable member to actuate said valve.

3. In Servo power brake mechanism, af

pedal, a lever pivoted to an arm thereof, a tension element connected to one arm of sa1d lever, a fluid pressure power device connected tive to said lever to actuate said valve whereto a second arm of said lever, a control valve, means whereby the movement of said lever about its pivot is limited and means operated by said pedal upon a movement thereof relaby the power device-.iis` rendered active -to rotate said lever.

4. The invention Vdefined by claim'3, said power device including a movable element and a piston rod, said valve beingassociated with said power device and the last mentioned means being a rod reci rocably concentric with reference to said pis on rod'.

5. The invention defined power device including a movable elementi together with ay piston rod, said valve'beingv associated. with said power devicev and the lastnamed means being a. rod reciprocable' concentrically with reference to said piston rod, said piston rod being formed with an annular space for'connection with a source of subatmosphericpressure' and said valve controlling the communication between said space and said power device.

6. A power brake operating mechanism comprising a manually operated lever having a pivot, a brakelever pivoted thereto at a point removed from the pivot of the manby claim 3 said:-

a power device onnected 'tosaid brake lever and a valve means operable by said manually operable lever upon-its movement relative to said brake lever;` l

.7. The invention defined by claim 6, said valve means being incorporated within said power device. 'A

8. The invention defined by claim 6, said power device including a movable piston and said valve means being associated with said piston.

9. In a Servo brake, a pedal, a brake lever, a power device, brake linkage, said power device and brake linkage being attached at spaced points to said brake lever, means to connect said brake lever at a point between the points of connection of said power device and linkage to an arm of said pedal, means affording a lost motion connection between said brake lever and pedal at a point removed from said last mentioned connection, a valve controlling the action of said power device and a member moved by relative movement of said pedal and brake lever to actuate said valve. A

10. The invention defined by claim 9, said last motion connection beingadjacent the pivot of said pedal.

l1. The invention defined by claim 9, said power device including a plunger and a plunger rod, said plunger rod being connected to said brake lever .and said valve device, having aociated therewith -a.rod, said rod being-concentric with said plunger rod and moved to engage byithe yend of said pedal.

12. In aServo brake; a manually operable lever, fulcrum means therefor and brake lever, power vmeans connected to said brake lever, a' brake .applying member 'also connected to saidbrake lever means vpi-votally connecting said levers at a point removed from said fulcrum means', a lost motion conconnection being removed rom said pivotally means, valve means controlled by ,'";.reletv'e'movement between said levers v"whereby the valve means is operable to 'render the power means active, said lost motion connection beingl positioned substanti# vally adjacent thep'ivot of said brake lever.

whereof I affix my signature.

' Intestimony -lGEORGE P. BERRY. 

